The present invention relates to a signal transmission technology of a vehicle.
Various vehicle driving technologies have been developed recently. For example, one of many onboard CPUs (Central Processing Units) which are installed to the vehicle is used as a main control part to control other CPUs totally. This main control part may be configured to determine various target values of a vehicle speed, a vehicle acceleration, a vehicle traveling direction, a braking force to be applied to the vehicle, or a traction to be transmitted to a road surface from the vehicle based on information provided from various onboard sensors or cameras. These target values determined by the main control part are transmitted to the other CPUs through wire harnesses (see Japanese Patent Laid-Open Publication No. 2014-34373).
The other CPUs are used as component control parts to control corresponding electric components (an engine, a transmission, a brake, or a steering, for example). The component control parts which receive the target values from the main control part control the corresponding electric components so that the target values of the speed, the acceleration, the traveling direction, the braking force, or the traction can be achieved.
According to the technology disclosed by the above-described patent document, the signal transmission from the main control part to the component control parts relies on a single signal transmission route. If the vehicle contacts an obstacle softly (another vehicle, for example) and the signal transmission route is shut down (damaged), the information transmission from the main control part to the component control parts may be stopped. In a case where the component control parts control the electric components for governing a drive of the vehicle, such as the engine, the transmission, the brake, or the steering, the above-described information-transmission stop may cause the loss of controls of basic motions of the vehicle, such as “vehicle advancing,” “vehicle retreating,” “vehicle traveling-direction changing,” or “vehicle stopping.”